Decreases in blood ethanol concentrations during storage at 4 °C for 12 months were the same for specimens kept in glass or plastic tubes

Blood alcohol concentration in the clinical laboratory: a narrative review of the preanalytical phase in diagnostic and forensic testing

The analysis of blood alcohol concentration (BAC), a pivotal toxicological test, concerns acute alcohol intoxication (AAI) and driving under the influence (DUI). As such, BAC presents an organizational challenge for clinical laboratories, with unique complexities due to the need for forensic defensibility as part of the diagnostic process. Unfortunately, a significant number of scientific investigations dealing with the subject present discrepancies that make it difficult to identify optimal practices in sample collection, transportation, handling, and preparation. This review provides a systematic analysis of the preanalytical phase of BAC that aims to identify and explain the chemical, physiological, and pharmacological mechanisms underlying controllable operational factors. Nevertheless, it seeks evidence for the necessity to separate preanalytical processes for diagnostic and forensic BAC testing. In this regard, the main finding of this review is that no literature evidence supports the necessity to differentiate preanalytical procedures for AAI and DUI, except for the traceability throughout the chain of custody. In fact, adhering to correct preanalytical procedures provided by official bodies such as European federation of clinical chemistry and laboratory medicine for routine phlebotomy ensures both diagnostic accuracy and forensic defensibility of BAC. This is shown to depend on the capability of modern pre-evacuated sterile collection tubes to control major factors influencing BAC, namely non-enzymatic oxidation and microbial contamination. While certain restrictions become obsolete with such devices, as the use of sodium fluoride (NaF) for specific preservation of forensic BAC, this review reinforces the recommendation to use non-alcoholic disinfectants as a means to achieve "error-proof" procedures in challenging operational environments like the emergency department.

Preanalytical factors influencing the results of ethanol analysis in postmortem specimens

Excessive drinking and drunkenness are underlying factors in many fatal accidents, which make the quantitative determination of ethanol in postmortem (PM) specimens an essential part of all unnatural death investigations. The same analytical methods are used to determine ethanol in blood taken from living and deceased persons although the interpretation of the results is more complicated in medical examiner cases owing to various preanalytical factors. The biggest problem is that under anaerobic conditions ethanol can be produced naturally in decomposed bodies by microbial activity and fermentation of blood glucose. Ways are needed to differentiate antemortem ingestion of ethanol from PM synthesis. One approach involves the determination of ethanol in alternative specimens, such as bile, cerebrospinal fluid, vitreous humor and/or urine, and comparison of results with blood alcohol concentration (BAC). Another approach involves the analysis of various alcohol biomarkers, such as ethyl glucuronide, ethyl sulfate and/or phosphatidylethanol or the urinary metabolites of serotonin 5-hydroxytryptophol/5-hydroxyindoleacetic acid (5-HTOL/5-HIAA). If ethanol had been produced in the body by microbial activity, the blood samples should also contain other low-molecular volatiles, such as acetaldehyde, n-propanol and/or n-butanol. The inclusion of 1-2% w/v sodium or potassium fluoride, as an enzyme inhibitor, in all PM specimens is essential to diminish the risk of ethanol being generated after sampling, such as during shipment and storage prior to analysis. Furthermore, much might be gained if the analytical cut-off for reporting positive BAC was raised from 0.01 to 0.02 g% when PM blood is analyzed. During putrefaction low BACs are more often produced after death than high BACs. Therefore, when the cadaver is obviously decomposed, a pragmatic approach would be to subtract 0.05 g% from the mean analytical result. Any remaining BAC is expected to give a more reliable indication of whether alcohol had been consumed before death.

Comparisons of blood alcohol concentrations between initial testing and reanalysis from unopened tubes preserved with 0.25% NaF following refrigerated storage up to 3.93 years

Few studies support the usage of <1% nominal sodium fluoride (NaF) to preserve ethanol in antemortem blood. Of these studies, several are limited by short study durations of 90 days or less, and there is limited research of authentic samples preserved with <1% NaF. In this retrospective analysis, data from initial and reanalysis testing of blood alcohol concentration (BAC) in antemortem blood collected in 6 mL gray-top tubes (providing 0.25% nominal NaF) has been compiled, to evaluate changes in ethanol concentration that occurred after periods of refrigerated storage. The time between initial and reanalysis was determined by court request(s), and ranged 0.30-3.93 years. In each case, a previously unopened tube was selected for reanalysis testing. Comparable BAC values were found from initial testing, with BACs ranging from 0.025 to 0.394 g/100 mL, and reanalysis testing, with BACs ranging from 0.021 to 0.393 g/100 mL. Ethanol changes ranged from -0.013 g/100 mL (decrease) to 0.008 g/100 mL (increase). BAC reanalysis values that increased (n = 6) were within the uncertainty of measurement (UM) from the initial BAC test, that is, were not statistically or analytically significant. For BAC decreases (n = 29), four test values exceeded the UM of the original test, with BAC losses ranging from 0.004 to 0.011 g/100 mL (relative percent changes 6.5-16.0% loss). The average ethanol change was -0.004 g/100 mL, which is comparable to or less than ethanol losses from studies using 1% NaF preservative of varying temperature and storage duration.

Ethanol stability in unpreserved refrigerated antemortem blood

Ethanol stability in preserved antemortem blood has been widely studied since it is a common practice in cases involving suspected impaired driving to collect antemortem blood in evacuated blood tubes containing sodium fluoride. In some situations, antemortem blood is submitted to a forensic laboratory for ethanol analysis in evacuated blood tubes that contain only an anticoagulant. There has been limited research on ethanol stability in antemortem blood stored without a preservative. On two occasions, antemortem blood was collected from five ethanol-free individuals into 6-ml Vacutainer® tubes containing only 10.8 mg potassium EDTA. The blood tubes were spiked with ethanol to approximately either 0.08 or 0.15 g/dl. Dual-FID headspace gas chromatography was used to analyze 58 blood tubes, 29 from each session, for ethanol 1 day after sample collection and again after 1 year of refrigerated storage (~4°C). Statistically significant decreases in ethanol were detected at the 0.05 level of significance. Mean decreases in ethanol after 1 year of storage for the 0.08 and 0.15 g/dl samples were 0.013 and 0.010 g/dl, respectively. The mean ethanol decrease across all tubes was 0.012 g/dl. The range of decreases for the 58 blood tubes was 0.003-0.018 g/dl. The mean ethanol decreases measured in this unpreserved antemortem blood are comparable in magnitude to those previously observed in antemortem blood containing sodium fluoride after 1 year of refrigerated storage. Ethanol did not increase in the antemortem blood samples despite the absence of sodium fluoride.

Statistical comparisons of 0.08 g/100 ml fortified blood alcohol samples from 6-ml and 10-ml gray-top tubes

This experiment supplements the study, "Statistical comparisons of blood alcohol samples from 6-ml and 10-ml grey-top tubes". The initial study analyzed fortified samples for blood alcohol concentration (BAC) using two sizes of gray-top tubes: a 10-ml tube containing a nominal 1% sodium fluoride (NaF), a preservative, and a 6-ml tube containing 0.25% NaF, using the variables of time, storage temperature, fill volume, and concentration. From that study, paired t-tests determined no difference in BAC from data sets of the two tube sizes, however, Analysis of Variance, or ANOVA, testing determined the two tube sizes yielded different results at 0.08 g/100 ml. To investigate this potential disparity, this study fortified new samples at 0.08 g/100 and focused on two variables: fill volume and storage duration, while increasing the sample population (to n = 8). For this study, the two tube types yielded equivalent concentrations under the majority of conditions studied. Differences between the two tube types were found using paired t-test for the high-volume samples on Days 7 and 30; ANOVA yielded the same results but also determined one additional statistical difference for the Day 30 low-volume samples. However, the differences observed between tube sizes fall within standard deviation ranges established for the analytical method precision profile, indicating statistical differences are not analytically significant. Further studies are needed to investigate the comparability of the tubes under real-world conditions, under which oxygen and/or additives are not added during sample preparation steps or by usage of blood bank products.

Lack of fermentation in antemortem blood samples stored unstoppered in various locations

A common defense challenge when antemortem blood ethanol results are presented at trial is the assertion that ethanol was formed in the blood tube after the blood draw through fermentation of the blood glucose by Candida albicans (C. Albicans). In contrast, decades of research into the stability of ethanol in antemortem blood collected for forensic purposes have consistently shown that any analytically significant change in ethanol concentration is a decrease and initially, ethanol-negative blood remains ethanol-negative with storage. For there to be any possibility of fermentation to occur by C. Albicans in an antemortem blood sample there must be a plausible mechanism for introduction of C. Albicans into the blood. One mechanism proffered at trial is environmental contamination resulting from ambient air drawn into the evacuated blood collection tube. Blood was drawn from ethanol-free individuals into 6 and 10-ml gray-top Vacutainer® tubes containing sodium fluoride and 6-ml Vacutainer® tubes without a preservative. Following the blood draws, the tubes were stored unstoppered at room temperature for 24 or 48 h in various locations. Following unstoppered storage, the tubes were stoppered and stored refrigerated (~4°C), left at room temperature (~22°C), or placed in an oven (37°C). The refrigerated blood was analyzed for ethanol using headspace gas chromatography after both 5 days and 32 months. Unrefrigerated blood samples were analyzed after being stored at room temperature or in an oven for up to 30 days. Ethanol was not detected in any of the blood tubes after storage regardless of storage time, storage temperature, or preservative concentration.

Spirited away: Can ethanol testing in add-on orders provide meaningful results?

Ethanol is a volatile substance, and specimens need to be tightly capped prior to analysis to prevent evaporative loss. However, add-on requests in previously decapped tubes are commonly received, yet ethanol stability in this setting is unclear. We compared the stability of ethanol in capped vs decapped tubes in the context of routine laboratory automation, storage time, and specimen volumes. Serum specimens were pooled and spiked with ethanol followed by simulating an add-on scenario. Additionally, to evaluate ethanol stability at room temperature for extended times, ethanol concentrations were measured in capped or decapped tubes containing 0.5 mL or 0.1 mL samples over a 4 h time course. Finally, the risk of misclassification of ethanol results in decapped tubes was evaluated near the critical value threshold (∼54 mmol/L). The add-on tubes had a mean recovery of 101.5 % (95 % CI: 97.7-105.4 %) relative to the direct tubes. The time-course experiment showed an average recovery of 87.4 % (95 % CI: 81.8-94.0 %) at the 4 h time point in decapped 0.5 mL specimens. An average recovery of 85.4 % (95 % CI: 84.2-86.1 %) was observed for specimens spiked near the critical value threshold. Importantly, all measurements with 0.5 mL specimen volume were within 25 %, which is the total allowable error (TAE) of the assay.However, with a 0.1 mL volume, specimens cross the TAE threshold just after 1 h, and the percent recovery at 4 h dropped to 52.9 % (95 % CI: 50.2-55.7 %). In conclusion, ethanol testing in decapped tubes remains within the TAE for up to 4 h in specimens with a 0.5 mL volume. Therefore, add-on ethanol testing using routine laboratory automation and storage conditions can be successfully performed.

Testing antemortem blood samples for ethanol after four to seven years of refrigerated storage

The previous studies on ethanol stability in antemortem blood samples stored under various conditions have shown that ethanol concentration decreases with storage. The feasibility of measuring a forensically meaningful blood ethanol concentration in antemortem blood samples stored refrigerated (~4°C) from 4-7 years after the blood draw was evaluated in this research. All blood samples were collected into two 10-ml gray top Vacutainer® tubes as part of police driving under the influence investigations. In 29 cases, blood in the tube originally analyzed was retested after 5-7 years of refrigerated storage. Blood in 41 cases was analyzed in a previously unopened blood tube from the case after 4-7 years of refrigerated storage. The first analysis of blood in each case occurred within 35 days of the blood draw. Initial blood ethanol concentrations ranged from 0.094 g/dl to 0.301 g/dl. No samples showed an increase in ethanol concentration with storage that exceeded the uncertainty of the initial measurement. All decreases in ethanol concentration were less than 0.020 g/dl. The mean differences in ethanol concentration in previously opened and unopened tubes were -0.014 g/dl and -0.010 g/dl, respectively. The results of this research support that antemortem blood in previously opened and unopened refrigerated blood tubes can be analyzed for ethanol content more than 4 years and as much as 7 years after the blood draw and provide a result consistent with the amount of ethanol loss expected from a test done within 1-3 years of the blood draw.

Re-analysis of suspected DWI blood samples for ethanol: A Texas case study

The gradual loss of ethanol over time in stored blood specimens under a variety of conditions has been well documented. An analysis of over 160 blood specimens from suspected impaired drivers was recently accomplished with the knowledge that the samples had previously been analyzed. These two analyses were performed independently, using different methods and instrumentation and by different individuals. Although in most cases there were two tubes available in each case, the tube used for the initial analysis was also used for the second analysis. Reported results from both laboratories were obtained and evaluated retrospectively. Over an average interval of approximately 13 months (range 34-1002 days), the average change of ethanol concentrations was a loss of 0.006 g/dL, with a maximum loss of 0.023 g/dL, and a maximum increase of 0.004 g/dL. The median difference was a loss of 0.005 g/dL. The percentage of samples that reported second concentrations equal to or less than the original reported concentrations (to the thousandths decimal place) was 96.4%. No correlation was observed between the net loss and the initial BAC value, but the amount of time between analyses did impact the extent of the loss of ethanol as determined by the second analysis. Our results indicate a smaller loss of ethanol, and hence stronger correlation between analytical events, than what has been experienced in similar work. Based on our analysis and review of previously opened and analyzed blood specimens, a previously opened blood tube can yield a strong correlation to the original analysis and may therefore be appropriate if a second tube is not available or compromised in some way.

Large-scale reanalysis of refrigerated antemortem blood samples for ethanol content at random intervals

Ethanol stability in antemortem blood stored under various conditions has been widely studied. Most such studies have somewhat limited sample size (<50) and limited variation in the length of time between the blood draw and the first analysis and between the first analysis and the reanalysis. In the work presented here, the antemortem blood drawn for forensic purposes and stored refrigerated (~4°C) in 371 cases was analyzed for ethanol concentration using headspace gas chromatography at various times after the blood draw based on routine case flow and then also analyzed at various times within approximately 1 year after the first analysis. This methodology is intended to provide insight into the range of differences expected when cases are analyzed in the normal flow of casework and then reanalyzed at random times afterwards as occurs when reanalysis is performed by the defense or by the laboratory if the original analyst is unavailable to testify. In 22 cases, the same blood tube from the case was reanalyzed. The previously unopened blood tube from the case was analyzed in 349 cases. The 25 cases in which the blood was ethanol-negative based on the first analysis remained ethanol-negative when reanalyzed. The average difference in ethanol concentration between tests for the ethanol-positive cases was -0.004 g/dL. This decrease was statistically significant at the 0.05 level of significance. The range of differences was -0.0197 to 0.0103 g/dL. The difference measured in 85% of the ethanol-positive cases was in in the range of -0.008 to -0.001 g/dL.

Inferences and Legal Considerations Following a Blood Collection Tube Recall

In mid-2019, medical, forensic and legal communities were notified that a certain shipment of evacuated blood sampling tubes were recalled by the manufacturer. This recall order described that the preservative sodium fluoride (100 mg) and anticoagulant potassium oxalate (20 mg) were missing from a small batch of 10-mL evacuated tubes. This gave cause for concern for possible implications in criminal justice (e.g., in drink-driving offenses) when blood-alcohol concentrations are interpreted. In reality, the lack of an anticoagulant would have been immediately obvious during sample preparation, owing to the formation of a large clot in the tube when received. Certain impairing drugs (e.g., cocaine and 6-acetylmorphine) are unstable in blood and tend to degrade without an enzyme inhibitor, such as sodium fluoride, present. In reviewing available literature related to current practices and the stability of ethanol in stored blood samples, there does not appear to be a clear consensus regarding the amount of sodium fluoride preservative necessary, if any at all, when blood is taken from living subjects under sterile conditions for typical forensic ethanol analysis.

Statistical comparisons of blood alcohol samples from 6-mL and 10-mL grey-top tubes

Historically, blood alcohol concentration (BAC) studies utilized a 1% concentration of the preservative sodium fluoride (NaF), leaving an information gap supporting usage of lower concentrations of NaF to preserve ethanol. As many forensic laboratories utilize Becton, Dickinson and Company 6-mL gray-top tubes (0.25% NaF), statistical comparisons were conducted to determine whether significant differences exist between BAC values obtained from 6-mL tubes versus 10-mL tubes (1% NaF). Whole blood was spiked at three concentrations, (0.04, 0.08, and 0.15 g/100 mL) and aliquoted into tubes at "low," "medium," and "high" fill volumes. Tubes were split into refrigerated or ambient storage and analyzed after 1, 3, 5, 7, and 30 days, using headspace gas chromatography. Each 6-mL and 10-mL tube pair, prepared, stored, and analyzed under identical conditions, was compared by t-test (95% confidence level). For refrigerated tubes, 32 of 45-tube pairs did not reject the null hypothesis (that 6-mL and 10-mL tubes yield equivalent BACs), and 31 of 45 ambient stored tube pairs did not reject the null hypothesis. Analysis of variance (ANOVA) found no significant differences between 6-mL and 10-mL gray-top tubes for 0.04 and 0.15 g/100 mL concentrations over 30 days; significant differences were observed for 0.08 g/100 mL concentration tubes, which warrants further study. Paired t-tests of grouped samples found no significant differences between 6-mL and 10-mL tubes at any concentration.

Testing Antemortem Blood for Ethanol Concentration from a Blood Kit in a Refrigerator Fire

The stability of ethanol in antemortem blood stored under various conditions has been widely studied. Antemortem blood samples stored at refrigerated temperature, at room temperature, and at elevated temperatures tend to decrease in ethanol concentration with storage. It appears that the stability of ethanol in blood exposed to temperatures greater than 38°C has not been evaluated. The case presented here involves comparison of breath test results with subsequent analysis of blood drawn at the time of breath testing. However, the blood tubes were in a refrigerator fire followed by refrigerated storage for 5 months prior to analysis by headspace gas chromatography. The subject's breath was tested twice using an Intoxilyzer 8000. The subject's blood was tested in duplicate using an Agilent headspace gas chromatograph. The measured breath ethanol concentration was 0.103 g/210 L and 0.092 g/210 L. The measured blood ethanol concentration was 0.0932 g/dL for both samples analyzed. Although the mean blood test result was slightly lower than the mean breath test result, the mean breath test result was within the estimated uncertainty of the mean blood test result. Even under the extreme conditions of the blood kit being in a refrigerator fire, the measured blood ethanol content agreed well with the paired breath ethanol test.

High Correlation between Ethanol Concentrations in Postmortem Femoral Blood and in Alternative Biological Specimens, but Large Uncertainty When the Linear Regression Model Was Used for Prediction in Individual Cases

In connection with medicolegal autopsies peripheral blood (e.g. from a femoral vein) is the specimen of choice for toxicological analysis, although alternative specimens are also sometimes submitted, such as bile, cerebrospinal fluid (CSF), vitreous humor (VH), bladder urine, pleural effusions and/or lung fluid. Ethanol concentrations were determined in duplicate in femoral blood and in various alternative biological specimens by headspace gas chromatography. The analysis was carried out on two different fused silica capillary columns furnishing different retention times for ethanol and both n-propanol and t-butanol were used as internal standards. The results were evaluated by linear regression using blood alcohol concentration (BAC) as dependent or outcome variable and the concentrations in an alternative specimen as independent or predictor variable. The Pearson correlation coefficients were all statistically highly significant (P &lt; 0.001); r = 0.94 (bile), r = 0.98 (CSF), r = 0.97 (VH), r = 0.92 (urine), r = 0.94 (lung fluid) and r = 0.96 (pleural cavity effusions). When the regression model was used to predict femoral BAC from the mean concentration in an alternative specimen the mean and 95% prediction intervals were 1.12 ± 0.824 g/L (bile), 1.41 ± 0.546 g/L (CSF), 1.15 ± 0.42 g/L (VH), 1.29 ± 0.780 g/L (urine), 1.25 ± 0.772 g/L (lung fluid) and 0.68 ± 0.564 g/L (pleural cavity effusions). This large uncertainty for a single new observation needs to be considered when alcohol-related deaths are evaluated and interpreted. However, the analysis of alternative specimens is recommended in medical examiner cases to provide supporting evidence with regard to the origin of ethanol, whether this reflects antemortem (AM) ingestion or postmortem (PM) synthesis.

Inter-laboratory proficiency results of blood alcohol determinations at clinical and forensic laboratories in Italy

BACKGROUND

Inter-laboratory proficiency schemes are widely used to control the performance of clinical and forensic toxicology laboratories. In 2016 the Laboratory of Environmental Hygiene and Forensic Toxicology - Venice (Italy) initiated an inter-laboratory proficiency test of blood-alcohol analysis. The number of participating laboratories gradually increased from 26 to 36. Furthermore, a few clinical laboratories were included if gas chromatographic (GC) methods were used for blood alcohol analysis.

PROCEDURE

Whole blood was obtained from the Blood Transfusion Centre of the Venice Hospital and a mixture of sodium fluoride and potassium oxalate was added as a preservative and anticoagulant, respectively. Aliquots of the blood were spiked with certified pure ethanol to obtain target blood-alcohol concentrations (BACs) ranging from 0 to 5.0g/L. Two blood samples (4mL each) were included in each shipment to the participating laboratories. The laboratories were asked to provide information about number of replicate BAC determinations they made, the types of ethanol reference standards used, and inherent measurement uncertainty. The aim of the testing was to obtain a mean consensus value for the target BAC and to assess inter-laboratory imprecision. All procedures for registration and submission of results were done on-line. A confidential report and statistical evaluations were returned to the participants one week later.

ANALYTICAL METHODS

All participants used head-space GC (HS-GC) for the analysis of ethanol in blood. More than 85% of participants used HS-GC with flame-ionization detection, whereas the others used mass spectrometry (MS) as a detector. More than 40% of the participating laboratories kept the blood samples frozen (-20°C) prior to analysis, whereas the others used refrigeration (+4°C). The preliminary validation tests showed that there were no statistically significant differences between BAC in frozen or refrigerated samples for a period of 20 days.

RESULTS AND CONCLUSION

The statistical evaluation of results was done using an iterative procedure known as Algorithm A (ISO 13528:2015, C.3.1). This provides robust estimates for mean and standard deviation between laboratories and these were used as consensus values. More than 85% of participants provided satisfactory results (z-score <1) and 94% of laboratories were within z-score <2, based on five control samples. When a blood sample without any alcohol (blank) was sent for analysis, laboratories reported this as zero, 0.00g/L, below limit of detection (LOD) or not detected. Some type of consensus should be reached for reporting blank samples.